Apparatus and method for forming relief portions in the periphery of a grinding wheel

ABSTRACT

This invention pertains to the dressing of face-formed grinding wheels and in particular diamond-faced grinding wheels wherein certain face portions may be at an acute angle to a plane normal to the axis of the grinding wheel. To drastically reduce the probability of burning the workpiece while contour grinding a selected portion of this workpiece, apparatus is provided to alter the periphery of the grinding wheel so that determined portions of said periphery of the grinding wheel are relieved. The grinding wheel face so contoured presents a series of faceforming segments by which the workpiece is ground. The dressing apparatus is selectively movable to and from a dressing condition of the periphery of the grinding wheel.

United States Patent m1 Swenson APPARATUS AND METHOD FOR FORMING RELIEFPORTIONS IN THE PERIPHERY OF A GRINDING WHEEL Jan. 2, 1973 1,700,6341/1929 Hopf ..5 1/206 R Priniary Examiner-Harold D. WhiteheadAttorney-Ralph R. Roberts [57] ABSTRACT This invention pertains to thedressing of face-formed grinding wheels and in particular diamond-facedgrinding wheels wherein certain face portions may be at an acute angleto a plane normal to the axis of the grinding wheel. To drasticallyreduce'the probability of burning the workpiece while contour grinding aselected portion of this workpiece, apparatus is provided to alter theperiphery of the grinding wheel so that determined portions of saidperiphery of the grinding wheel are relieved. The grinding wheel face socontoured presents a series of face-forming'segments by which theworkpiece is gr0und.'The dressing apparatus is selectively movable toand from a dressing condition of the periphery of the grinding wheel.

Claims, 2 Drawing Figures PATENTED M' 2 m 3 707 956 INVENTOR.

HENRY F SWENSON "'7 f v ((141.4. 4,5, AGENT APPARATUS AND METHOD FORFORMING RELIEF PORTIONS IN THE PERIPHERY OF A GRINDING WHEEL CROSSREFERENCE TO A RELATED APPLICATION The apparatus for forming reliefportions in the periphery of a'grinding wheel may be, and preferably is,used with apparatus for contour dressing a grinding wheel as shown anddescribed in U.S. Patent Application entitled, Grinding Wheel DressingApparatus" and given Ser. No. 63,060 when filed Aug. 12th, 1970 in thename of Henry F. Swenson who is also the applicant for this application.

BACKGROUND OF THE INVENTION development began more than a century ago.Contour grinding by precisely shaping the face of the grinding wheelbefore and during the grinding of portions of the workpiece has becomean established machining method developed within the last few decades. Aproblem which has plagued this contour grinding method of machining hasbeen the tendency of burning the workpiece when the angle of a facepor-' tion of the grinding wheel approaches a condition near rightangles to the axis of the grinding wheel rotation. This condition occurswhen there is a tendency for the face of the grinding wheel to rub theworkpiece surface being ground. There is also a tendency for burning thework when the grit of the grinding wheel is quite fine and tends toglaze during the grinding of the workpiece as when it is necessary for amicro" finish of '8 r.m.s. (root means square) micro-inches or better tobe formed on the workpiece.

- This problem of burning is largely solved or at the least is greatlyreducedby the method of forming a series of recessed contours into theperiphery of a grinding wheel by the apparatus provided by thisinvention. Whereas, a contour-faced grinding wheel conven tionally hasits entire periphery precisely formed and radially disposed around theaxis of the grinding wheel, this invention includes an additionalforming step.

After initially forming the face of the grinding wheel to grindingresidue to be dispersed and distributed particularly at the impingementnip of the grinding wheel and workpiece. The engagement of the face ofthe grinding wheel with the workpiece, instead of being continuous is bythe relieved grinding of this invention reduced to intermittentengagement periods which are preferably regular and which enable theworkpiece, at the area of grinding, to be kept at a substantially coolertemperature.

2 BRII-EF SUMMARY OF THE INVENTION This invention may be summarized atleast in part with reference to its objects.

It is an object of this invention to provide, and it does provide,apparatus pivotally supported so that in response to a predetermined camarrangement a previously form-shaped grinding wheel may have itsperipherial grinding surfaces portion formed with a plurality of reliefportions which are at least a few thousandths of an inch below thepreviously dressed surface of the grinding wheel.

It is a further object of this invention to provide, and it doesprovide, a pivotally mounted grinding wheel dressing apparatus disposedto carry shaping means for forming the face of the grinding wheel, saidapparatus further having a follower arm adapted to ride on a rotary camcarried by and rotated with the spindle upon which is mounted thegrinding wheel; said cam being contoured so that the engaged andsupported follower arm is raised and lowered by the contour of the camto form a plurality of relief portions in the peripherial face of thegrinding wheel.

It is a still further object of this invention to provide, and it doesprovide, a method for forming determined relief portions of a grindingwheel including the steps of supporting grinding wheel dressingapparatus so as to be movable toward and to the grinding wheel carriedon the grinding machine; attaching a follower arm on the dressingapparatus; mounting a lobed circular cam on the spindle ofthe grindingmachine, and arranging a follower roller on the follower arm so as toride on the lobes of the cam to limit movement of the dressing apparatustoward the grinding wheel while the movement which provides the meansfor limiting the movement of the dressing apparatus into the grindingwheel is manipulated to permit the roller, after leaving a lobe, to

- lobes and recesses is removably mounted on the retain-' ing nutmounted on the outer end of the spindle of the grinder. The cam followeris adjusted to rest upon the periphery of the cam after the dressingmechanism has been used to complete the dressing of the grinding wheel.The cam follower is caused to bear on the lobes of the cam to lift thedressing means from the grinding wheel and when the cam follower isbrought in way of and enters the recesses of the cam the grinding wheelis permitted to dress these local areas of the grinding wheel to providerecesses in the grinding wheel surface. The depth of the severalrecesses is usually each alike and of several thousandths of an inch.

In addition to the above summary the following disclosure is detailed toinsure adequacy and aid in understanding of the invention. Thisdisclosure, however, is not intended to prejudice that purpose of apatent which is to cover each new inventive concept therein no matterhow it may later be disguised by variations in form or additions offurther improvements. For this reason there has been chosen a specificembodiment of the apparatus for forming relief portions in the peripheryof a grinding wheel as adopted for use with contoured grinding wheeldressing and showing a preferred means for mounting a lobed cam on thespin-. 7

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 represents a side view of alobed cam and a follower support arm of this apparatus in mountedcondition on a pivoted dressing apparatus as shown in phantom outline,and

FIG. 2 represents an end view of the apparatus of FIG. 1 with thegrinding wheel shown with its periphery contoured and in solid outlineprior to its being relieved by the apparatus of the invention.

In the following description and in the claims various details will beidentified by specific names for convenience; these names, however, areintended to be generic in their application. Corresponding referencecharacters refer to like members throughout the two figures of thedrawing.

The drawing accompanying, and forming part of, this specificationdiscloses certain details of construction forthe purpose of explanationof the broader aspects of the invention, but it should be understoodthat structural details may be modified in various respects withoutdeparture from the concept and principles of the invention and that theinvention may be incorporated in other structural forms than shown.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in particular tothe drawing and the apparatus depicted in FIGS. 1 and 2, there is to beseen in phantom outline a frame 10 of a grinding wheel dressingapparatus such as that shown in my application Ser. No. 63,060, filedAug. 12th, 1970. To the extent necessary to show and describe contourdressing of grinding wheels, application, Ser. No. 63,060, isincorporated by reference into the instant application. This frame 10 orupper housing is pivotally supported on a base 12 attached to thegrinding wheel machine. Base 12 is also shown in phantom outline and maybe removably attached to the grinding machine by means disclosed in thereference patent. A micrometer screw 14 is disposed to limit and controlthe downward movement of frame 10 toward base 12 and is preciselyadjusted to enable shaping wheel to form and dress the periphery 22 ofagrinding wheel 24 (FIG. 2).

A follower arm 30 has a roller or ball bearing type cam follower 32rotatably carried on its lower end. The upper end of arm 30 is formedwith slots 34 and 35 through which the shank and threaded portion of aturnscrew 36 is passed for mounting the arm 30 on frame l0. The threadedend 38 of turnscrew 36 is retained in a threaded hole formed in frame 10while the headed end portion of the turnscrew 36 is disposed to engagethe outer face of the follower arm. When the turnscrew is tightened inthe threaded hole it retains the follower arm 30 in a selected fixedcondition and position on the frame.

A cam 40, as depicted, is a disc-like member having a bore 42 sized toslide on and be retained'on the outer diameter of a retaining nut 44which conventionally provides the means for retaining the grinding wheel24 on a spindle 46 of the grinding machine. A set screw 48 is carried ina threaded transverse hole in cam 40 and is tightened in the hole toretain cam 40 on nut 44. As

shown, the cam 40 is formed with four lobes 50 of like radius and eachis of an extent equal to about one? eighth of the diameter of the cam.

Between lobes 50 are formed recess portions 52 which are also preferablyof a like configuration. These recesses are madeat least aboutone-thirty-second to one-eighth of an inch radially less than theoutersurface of lobes 50. The width or thickness of the cam 40 is madesufficiently ample so that roller 32 may be positioned to easily ride onthe periphery of the cam 40.

USE AND OPERATION OF THE RELIEF FORMING APPARATUS To use the reliefforming apparatus of this invention it is necessary that there beprovided a grinding wheel dressing device which preferably is similar ifnot identical to the apparatus shown in my US. Patent application, Ser.No. 63,060. During the dressing or forming of the periphery 22 ofgrinding wheel 24 by shaping wheel 20 the follower arm 30 is eitherremoved from frame 10 or is slid outwardly in slot 34 or 35 so that camfollower 32 is away from any possible engagement with cam 40. Micrometerscrew 14 is manipulated to progressively lower wheel 20 into dressingcondition until the grindingwheel 24 hasbeen brought to the desireddressed condition. Screw 14 is then manipulated to lift wheel 20 a fewthousandths of an inch from this final dressing condition.

With shaping .wheel 20 in this lifted condition, the turnscrew 36'isloosened so that follower arm 30 may he slid along the slot 34 or 35 andtoward cam 40. The follower arm 30 is advanced until follower roller 32engages the peripherial surface of a lobe 50 whereupon turnscrew 36 istightened to retain arm 30 in this adjusted condition. To insure thatthis tightened condition is at the desired setting the screw 14 ismanipulated to lower frame 10 a couple of thousandths of an inch towardbase 12 whereupon the spindle 46 and mounted grinding wheel 24 arerotated a couple of timesv to insure that roller follower 32 engages andrests on each lobe 50 as the cam 40 is rotated with the wheel 24 andthat when the follower rests on a lobe the dressing apparatus does notengage the grinding wheel just dressed.

Having establishedthat the arm 30 and the follower roller 32 are at thedesired setting, the grinding wheel is once more rotated at thedetermined dressing speed and the shaping wheel 20 is again rotatedatits desired dressing speed. Micrometer screw 14 is now rotated so thatshaping wheel 20 moves into and dresses the grinding wheel 24 to providerecess portions every time follower roller 32 leaves lobe 50 and dropsinto one of the recess portions 52. The micrometer screw 14 is continuedto be manipulated to permit shaping wheel 20 to form recesses untilabout fifteen thousandths of an inch is removed from the grinding wheelat the four arc portions corresponding to the four recesses 52. At theportions corresponding to the lobe portions of the cam the grindingwheel remains as formed since the roller engages each lobe to liftshaping wheel 20 from forming or dressing contact with grinding wheel24.

After the desired depth of the recesses has been established in theperiphery of the grinding wheel, the frame is lifted to disengageshaping wheel 20. Arm 30 may be removed, if desired, after which theshaping and finishing of the workpiece is accomplished by grinding inthe usual manner. The recesses in the face of the grinding wheel 24permit the grinding of the workpiece to be accomplished at a much coolertemperature and with a greater flooding of coolant on the workpiecesurface being ground. This grinding method is particularly effectivewhere the grinding grit of wheel 24 is quite fine and/or the surface ofthe workpiece being ground is at an acute angle to a plane normal to theaxis of spindle 46.

There has been shown two slots 34 and 35 in the upper portion offollower arm 30. Only one slot is used at one time but slot 35 permitsthe cam follower 32 to be moved leftwardly to engage the periphery ofcam 40 when cam 40 has been moved leftwardly or outwardly when retainingnut 44 is moved outwardly to retain a thicker grinding wheel 24.

Although the preferred apparatus for forming the grinding wheel 24 isthe apparatus shown and described in my application, Ser. No. 63,060, itdoes not follow that this is the only apparatus with which the presentinvention may be used. Other apparatus may be provided wherein thedressing or shaping wheel or means is pivotally supported so that it isfreely movable by gravity toward the grinding wheel and is readilylifted by arm 30 as follower 32 engages a lobe 50.

It is also contemplated that the dressing means 20, instead of beingpivotally retained, may be carried on a substantially vertical slide orguide means and by gravity be advanced to and into the grinding wheel24. Relief portions are similarly made in the grinding wheel by thedressing means as it is lifted from the grinding wheel by followerroller 32 as it engages a lobe 50.

Although primarily directed toward use in apparatus.

for contour shaping of the periphery of the grinding wheel, this reliefforming of a grinding wheel may also be used with grinding wheels whosefaces are straight or angle dressed. Desirably the recesses are formedgenerally symmetrical so as to keep the grinding wheel generally inbalance, although quite a variation in the balance of the wheel can bemade without vibrations developing in most grinding machine spindles.Ultra precision fit of bore 42 on nut 44 of the forming and dispositionof lobes 50 and recesses 52 is not necessary as the unbalance of therecessed grinding wheel is generally so slight that this small unbalanceof the grinding wheel does not affect the grinding accuracy or finish.

It is noted that instead of a separate cam 40 the nut 44 may have lobesand recesses formed on its periphery so while an integral member, itstill provides a lobe cam.

The above-described apparatus also provides a method for formingdetermined relief portions in the periphery of a grinding wheel whileand as it is carried on the spindle of a grinding machine, this methodincluding the steps of supporting a grinding wheeldressing apparatus ona grinding machine so that the dressing apparatus is pivotally movabletoward and away from the grinding wheel as it is carried on the spindleof a grinding machine; mounting a circular cam having a plurality oflobes and relief portions on the spindle of the grinding machine so thatthe cam is rotated as the spindle is turned; attaching a follower arm tothe grinding wheel dressing apparatus so that a roller follower carriedby and on the distal or lower end of said follower arm is disposed toengage and ride on the lobes of the circular cam to limit the movementof the dressing apparatus toward and to the grinding wheel as the rollerengages a lobe, and finally there is provided the step of selectivelylimiting the movement of the dressing apparatus into the grinding wheelto dress a plurality of recesses into the periphery of the grindingwheel at local extents corresponding to the recesses formed in theperiphery of the cam at those portions between lobes.

Terms such as left, right, up, down, bottorn, top, front, back, in,out", and the like are applicable to the embodiment shown and describedin conjunction with the drawing. These terms are merely for the purposesof description and do not necessarily apply to the position in which therecess forming apparatus may be constructed or used.

While aparticular embodiment of the recess forming apparatus has beenshown and described. it is to be understood the invention is not limitedthereto since modifications may be made within the scope of theaccompanying claims and protection is sought to the broadest extent theprior art allows.

What is claimed is:

1. Apparatus for forming determined relief portions in the periphery ofa grinding wheel as used on a grinding machine, said relief portionsproviding discontinuations in the prepared peripheral grinding surfacesin and on the face of said wheel, said relief forming apparatusincluding: (a) a grinding wheel dressing ap paratus adapted to dress theperiphery of a grinding wheel as said grinding wheel is carried on androtated with a spindle of a grinding machine, said dressing apparatusadapted to form the periphery of the wheel to a selected diameter andconfiguration; (b) means for supporting the dressing apparatus in ahinged manner so that the movable portion thereof is movable toward andaway from the wheel and so that a dressing portion may be broughtselectively into engagement with the grinding wheel; (c) adjustablemeans for limiting the movement of said dressing apparatus toward thegrinding wheel for forming and dressing a continuous. peripheral surfaceon said grinding wheel; (d) a circular cam having a plurality ofrecesses formed on its outer periphery to provide lobes on said cam; (e)

means for mounting said cam on the spindle carrying I the grinding wheelso as to turn with said spindle and grinding wheel with the mounted camdisposed so that to engage each of the lobes and when in engagementtherewith to support the dressing apparatus at-a determined disengagedposition above the dressed periphery of the grinding wheel, and (g)means for adjusting said limiting means and said follower arm topositions whereat when the roller of the follower arm is engaged by alobe of the rotating cam the dressing apparatus is supported so as to beout of contact with the grinding wheel and when the cam is furtherrotated and the roller is brought from a lobe and in way of a recess,the dressing apparatus to the limit controlled by the adjusted limitingmeans moves toward the grinding wheel permitting the dressing apparatusto locally engage and further dress the grinding wheel to form arelieved surface of the grinding wheel periphery which is below thepreviously dressed periphery of the grinding wheel, the length of therelief corresponding to the length of the recess in the cam.

2. Apparatus for forming determined relief portions in a grinding wheelas in claim 1 in which the grinding wheel dressing apparatus includes abase and a frame maintained in a pivotal relationship to eachother andwith the follower arm removably mountable on the movable member of thedressing apparatus.

3. Apparatus for forming determined relief portions in a grinding wheelas in claim 2 in which the cam is removably mountable on a retaining nutproviding means for retaining the grinding wheel on the spindle.

4. Apparatus for forming determined relief portions in a grinding wheelas in claim 2 in which the movable member is the upper frame member andthere is provided a micrometer screw carried in a threaded hole in theframe and disposed to engage the base to provide the means for limitingthe movement of the dressing apparatus toward the grinding wheel.

5. Apparatus for forming determined relief portions in a grinding wheelas in claim 4 in which the follower arm is provided with at least oneslot formed in its upper extent, and in which there is provided aturnscrew carried in a threaded hole in the frame, said turnscrew havingits shank disposed to be slidably retained in said slot while its headportion is adapted to engage the outer surface of the follower arm toretain said arm against the frame when the turnscrew is tightened in thethreaded hole in the frame.

6. Apparatus for forming determined relief portions in a grinding wheelas in claim 5 in which there is provided in the follower arm a pair ofslots in substantially parallel arrangement with one slot aligned sothat its axis passes through the roller on thearm.

7. Apparatus for forming determined relief portions in a grinding wheelas in claim l in which the lobes on the circular cam form arcs which areat least one-sixteenth of an inch greater in radius than are the radialdimensions of the arcs forming the recesses of the cam.

8. A method for forming relief portions of determined extent and depthin the periphery of a grinding wheel while and as it is carried on thespindle of a grinding machine, said relief portions providingdiscontinuations in the prepared peripheral grinding surfaces in and onthe face of said wheel, said method including the steps of: (a)supporting a grinding wheel dressing apparatus adapted to dress theperiphery of the grinding wheel on a grinding machine so that thisdressing ll l mll vfifiiefilii d lti l'ivg'll'fir til glllltimg wheel;(b) mounting a circular cam having a plurality of lobes and reliefportions therebetween on the spindle of the grinding machine so that theaxis of this cam coincides with the axis of the grinding wheel andretaining said'cam on the spindle so that this cam is rotated as thespindle is turned; (c) supporting the grinding wheel dressing apparatusby an adjustable follower arm having a roller carried on its distal endand with said roller disposed to engage and ride on the periphery of thecircular cam; (d) adjusting said arm so that when the roller is broughtinto supporting engagement of said lobes the dressing apparatus is notin dressing engagement with the wheel, and (e) adjusting an adjustablestop provided on the dressing apparatus to limit the movement of thefollower roller into the relief portions of the cam and when the rolleris in a relief portion between lobes to dress a recess into theperipheral grinding surface corresponding to the extent of reliefportion formed on the cam and with the depth of dressed recesscorresponding to the adjustment of the adjustable stop. i

9. A method for forming determined relief portions on a grinding wheelas in claim 8 in which the step of adjusting an adjustable stop forlimiting the movement of the dressing apparatus toward the grindingwheel is by manipulating a micrometer screw rotatably carried by thedressing apparatus and disposed to support a movable frame portion ofthe dressing apparatus above a fixed member of the dressing apparatus.

10. A method for forming determined relief portions on a grinding wheelas in claim 9 in which the mounting of the circular cam is on theperiphery of a retaining nut carried on the end of the spindle of thegrinding machine, and in which the attaching of the follower arm to thedressing apparatus includes arranging the follower arm so that a slot insaid arm is disposed-to be engaged by a shank of a turnscrew which isloosened for adjustment and removal of the follower arm and is tightenedto maintain saidarm in a determined position on said frame.

a a k =0:

1. Apparatus for forming determined relief portions in the periphery ofa grinding wheel as used on a grinding machine, said relief portionsproviding discontinuations in the prepared peripheral grinding surfacesin and on the face of said wheel, said relief forming apparatusincluding: (a) a grinding wheel dressing apparatus adapted to dress theperiphery of a grinding wheel as said grinding wheel is carried on androtated with a spindle of a grinding machine, said dressing apparatusadapted to form the periphery of the wheel to a selected diameter andconfiguration; (b) means for supporting the dressing apparatus in ahinged manner so that the movable portion thereof is movable toward andaway from the wheel and so that a dressing portion may be broughtselectively into engagement with the grinding wheel; (c) adjustablemeans for limiting the movement of said dressing apparatus toward thegrinding wheel for forming and dressing a continuous peripheral surfaceon said grinding wheel; (d) a circular cam having a plurality ofrecesses formed on its outer periphery to provide lobes on said cam; (e)means for mounting said cam on the spindle carrying the grinding wheelso as to turn with said spindle and grinding wheel with the mounted camdisposed so that the peripheral surfaces of the lobes are substantiallyequally distant from the axis of the spindle; (f) an adjustable followerarm removably retained on the grinding wheel dressing apparatus, saidarm having a roller rotatably mounted on its distal end, this rolleradapted to ride on the lobes of the cam when the arm is mounted on thedressing apparatus and is moved toward and into engagement with a lobeof the cam, and after the arm is fixed in the condition for the rollerto engage each of the lobes and when in engagement therewith to supportthe dressing apparatus at a determined disengaged position above thedressed periphery of the grinding wheel, and (g) means for adjustingsaid limiting means and said follower arm to positions whereat when theroller of the follower arm is engaged by a lobe of the rotating cam thedressing apparatus is supported so as to be out of contact with thegrinding wheel and when the cam is further rotated and the roller isbrought from a lobe and in way of a recess, the dressing apparatus tothe limit controlled by the adjusted limiting means moves toward thegrinding wheel permitting the dressing apparatus to locally engage andfurther dress the grinding wheel to form a relieved surface of thegrinding wheel periphery which is below the previously dressed peripheryof the grinding wheel, the length of the relief corresponding to thelength of the recess in the cam.
 2. Apparatus for forming determinedrelief portions in a grinding wheel as in claim 1 in which the grindingwheel dressing apparatus includes a base and a frame maintained in apivotal relationship to each other and with the follower arm removablymountable on the movable member of the dressing apparatus.
 3. Apparatusfor forming determined relief portions in a grinding wheel as in claim 2in which the cam is removably mountable on a retaining nut providingmeans for retaining the grinding wheel on the spindle.
 4. Apparatus forforming determined relief portions in a grinding wheel as in claim 2 inwhich the movable member is the upper frame member and there is provideda micrometer screw carried in a threaded hole in the frame and disposedto engage the base to provide the means for limiting the movement of thedressing apparatus toward the grinding wheel.
 5. Apparatus for formingdetermined relief portions in a grinding wheel as in claim 4 in whichthe follower arm is provided with at least one slot formed in its upperextent, and in which there is provided a turnscrew carried in a threadedhole in the frame, said turnscrew having its shank disposed to beslidably retained in said slot while its head portion is adapted toengage the outer surface of the follower arm to retain said arm againstthe frame when the turnscrew is tightened in the threaded hole in theframe.
 6. Apparatus for forming determined relief portions in a grindingwheel as in claim 5 in which there is provided in the follower arm apair of slots in substantially parallel arrangement with one slotaligned so that its axis passes through the roller on the arm. 7.Apparatus for forming determined relief portions in a grinding wheel asin claim 1 in which the lobes on the circular cam form arcs which are atleast one-sixteenth of an inch greater in radius than are the radialdimensions of the arcs forming the recesses of the cam.
 8. A method forforming relief portions of determined extent and depth in the peripheryof a grinding wheel while and as it is carried on the spindle of agrinding machine, said relief portions providing discontinuationS in theprepared peripheral grinding surfaces in and on the face of said wheel,said method including the steps of: (a) supporting a grinding wheeldressing apparatus adapted to dress the periphery of the grinding wheelon a grinding machine so that this dressing apparatus when carried onthe grinding machine is pivotally movable toward and away from thegrinding wheel; (b) mounting a circular cam having a plurality of lobesand relief portions therebetween on the spindle of the grinding machineso that the axis of this cam coincides with the axis of the grindingwheel and retaining said cam on the spindle so that this cam is rotatedas the spindle is turned; (c) supporting the grinding wheel dressingapparatus by an adjustable follower arm having a roller carried on itsdistal end and with said roller disposed to engage and ride on theperiphery of the circular cam; (d) adjusting said arm so that when theroller is brought into supporting engagement of said lobes the dressingapparatus is not in dressing engagement with the wheel, and (e)adjusting an adjustable stop provided on the dressing apparatus to limitthe movement of the follower roller into the relief portions of the camand when the roller is in a relief portion between lobes to dress arecess into the peripheral grinding surface corresponding to the extentof relief portion formed on the cam and with the depth of dressed recesscorresponding to the adjustment of the adjustable stop.
 9. A method forforming determined relief portions on a grinding wheel as in claim 8 inwhich the step of adjusting an adjustable stop for limiting the movementof the dressing apparatus toward the grinding wheel is by manipulating amicrometer screw rotatably carried by the dressing apparatus anddisposed to support a movable frame portion of the dressing apparatusabove a fixed member of the dressing apparatus.
 10. A method for formingdetermined relief portions on a grinding wheel as in claim 9 in whichthe mounting of the circular cam is on the periphery of a retaining nutcarried on the end of the spindle of the grinding machine, and in whichthe attaching of the follower arm to the dressing apparatus includesarranging the follower arm so that a slot in said arm is disposed to beengaged by a shank of a turnscrew which is loosened for adjustment andremoval of the follower arm and is tightened to maintain said arm in adetermined position on said frame.